Much interest has been created by the recent advances in the production of nanocomposites, nanometer sized dispersions of organophilic clays in polymers that form polymeric hybrids. Nanocomposites have been demonstrated to produce dramatic improvements in mechanical properties, heat resistance, thermal stability, and reduced gas permeability of the base polymer without loss of impact strength. Due to their enhanced barrier properties and clarity, nanocomposites are well suited for use as gas transport barriers in packaging applications. Examples include nylon-based nanocomposites for food and beverage packaging which incorporate the nanocomposite layer within single or multi-layer films. Reduction in gas diffusion is attributed to the presence of the clay particles which act to increase diffusion path length.
Typically, the organoclays used in nanocomposites are prepared by contacting an aqueous-based slurry of purified clay with various organic compounds, such as water-soluble polymers and surfactants. Present processing techniques require the organoclays to be recovered from the slurry and dried to a low moisture level before the organoclays may be processed further. Film drying and spray drying are the usual methods for attaining a low moisture level in the organoclays. However, the organoclays are very retentive of water and drying the organoclays to a moisture level suitable for further processing can be difficult, thermal energy intensive, time consuming, and expensive. In fact, the energy used to evaporate the large amounts of water associated with organoclay slurries and filter cakes accounts for approximately one third of the cost for making the organoclays that are used to produce nanocomposites by using conventional techniques.
Thus, a need exists for a method of preparing nanocomposites that eliminates or reduces the need for drying organoclays prior to their incorporation into a nanocomposite matrix.